For the past couple of years, Mr Hockey has been appearing alongside Labor frontbencher Tony Burke, but the cabinet minister was sent an email yesterday advising him he was no longer required.

Mr Rudd's return has prompted the usual speculation about his motives and whether he still harbours leadership ambitions.

His spokesman has told ABC News Online that Channel Seven approached Mr Rudd last year but he declined the invitation to come back on the show.

"He was approached again at the start of this year and as it is an election year Mr Rudd accepted," the spokesman said in a statement.

"As Mr Rudd has said consistently, he will do whatever he can in Queensland, around the country and through the media to argue for the Government's re-election, and that includes on Sunrise."

When today's discussion turned to current political issues, Mr Rudd defended Julia Gillard's decision to announce the election date more than seven months ahead of polling day and rejected suggestions there was a link to Craig Thomson's arrest yesterday.

"I'd be highly surprised if anyone knew of the activities of the police in what they did with Craig Thomson yesterday," he said.

"Look, the Prime Minister has named a date. That's her prerogative. She's the Prime Minister. That's what heads of government get to do."

He added that he was a supporter of four-year fixed terms but noted that it would require constitutional change.

The pair was then asked about the Coalition's decision to axe the School Kids Bonus if it won this year's election.

Mr Hockey said it was nothing the Coalition took any great pleasure in but argued that it was being paid for with borrowed money and had nothing to do with education.

Mr Rudd responded with an attack lasting more than a minute, prompting Mr Hockey to declare: "Now I know Kevin's back!"